U.S. Pat. No. 4,156,666 discloses degradable polyolefin resin compositions comprising the polyolefin resin, about 0.2 to 10% by weight of a fatty acid or esters of fatty acids with monohydric aliphatic alcohols and optionally, about 10 to 60% by weight of an inorganic filler such as calcium carbonate. These resins are clearly characterized as molding resins and the acid or esters are promoters for photodegradability. The degradation of the molding resins disclosed requires exposure to sunlight for degradation to occur.
It is well documented that the first issue regarding degradable plastics is the definition of "degradable". The classification of environmentally degradable materials was made by R. Narayan of Michigan Biotechnology Institute in "Degradable Materials: Perspectives, Issues and Opportunities", pg. 1, CRC Press, 1990, as "biodegradable, photodegradable and chemically degradable." The question was posed: "Are they (degradable plastics) a delusion, a solution or a downright hoax?" in an article by John Donnelly, "Degradable Plastics", Garbage, May/June 1990. As described in the article, the first attempts at producing a degradable polyolefin film, trash bags for example, was to add materials such as starch or sugar which made the plastic more biodegradable or to add materials such as metals which made the plastic more photodegradable. However, each of these materials were dependant on the environment of the plastic; for example the presence of bacteria for the biodegradable reaction to occur or sunlight (UV) for the photodegradable reaction to occur.
The present invention is directed to a combination of additives which produce a chemical degradation of the plastic over a period of time. The compounding of the additives to the plastic resins permits the desired use, trash bag or agricultural film, but will by chemical reaction cause the plastic product to be environmentally degradable. This chemical reaction is accelerated by heat and/or UV light but will degrade without sunlight when heated to temperatures such as found when the plastic is buried in landfills.